Chemical reaction system of electrochemical cell type, method for activation thereof and method for reaction

ABSTRACT

The present invention relates to a chemical reaction system for efficiently excluding nitrogen oxides with low power consumption when excess oxygen is present in exhaust gas, to a method of use therefor, to an activation method therefor, and to a reaction method for oxidizing or reducing by the use of an oxidation-reduction reactor with high selectivity without the need to supply or exchange a reducing agent or oxidizing agent.

TECHNICAL FIELD

The present invention relates to an electrochemical cell-type chemicalreaction system, and more specifically relates to a chemical reactionsystem which efficiently excludes nitrogen oxides from exhaust gascontaining oxygen. The present invention is useful in that it provides anovel chemical reactor which has micro reaction regions for performingoxidation and reduction reactions on a target substance introduced intopart of the chemical reaction part of the aforementioned chemicalreaction system so that oxygen and nitrogen oxides are separated andadsorbed from exhaust gas by particular structures within theaforementioned micro reaction regions, thus allowing a target substanceto be efficiently processed with low electric power consumption.

Moreover, the present invention relates to an energy-savingelectrochemical reaction system and an activation method therefor, andrelates more particularly to a chemical reaction system whichefficiently excludes nitrogen oxides from exhaust gas containing oxygenfor example, and to a method of use and activation method therefor. Thepresent invention is useful in that it provides a new chemical reactionsystem, along with a method of use and an activation method therefor,wherein when reactivity has been reduced by adsorption of oxygen atomson the surface during exclusion of nitrogen oxides from exhaust gas inthe electrochemical reaction system, the aforementioned chemicalreaction system can be reactivated with low power consumption, thusallowing efficient chemical reaction of the target substance.

Moreover, the present invention relates to a reaction method using anoxidation-reduction reactor, and relates more particularly to a chemicalreaction method of oxidizing organic matter, organochlorine compounds,hydrogen, carbon monoxide, nitrogen oxides, ammonia and the like forexample or a chemical reaction method of reducing organic matter,oxygen, water, nitrogen oxides and the like using an oxidation-reductionreactor composed of a solid electrolyte which is an oxygen ion conductorand at least an electrode consisting of an electron conductor. Thepresent invention is useful in that it provides a method of removingnitrogen oxides from the exhaust gas of burners and the like for exampleusing the aforementioned oxidation-reduction reactor.

BACKGROUND ART

At present, the principal method of excluding nitrogen oxides producedby gasoline engines is with ternary catalysts. However, because theexhaust gas from lean burning engines and diesel engines, which allowimproved fuel consumption, contains an excess of oxygen, reduction ofcatalytic activity due to adsorption of oxygen by the surface of theternary catalyst is a problem, preventing exclusion of nitrogen oxides.

On the other hand, by applying a flow of current to a solid electrolytefilm having oxygen ion conductivity removal is also accomplished withoutcausing adsorption of oxygen from the exhaust gas by a catalyst surface.One proposal for a catalytic reactor is a system which simultaneouslyremoves surface oxygen and breaks down nitrogen oxides into oxygen andnitrogen by applying voltage to a solid electrolyte sandwiched betweenelectrodes on both sides.

However, the problem is that in the aforementioned method if there is anexcess of oxygen in the exhaust gas, because the adsorption anddecomposition reaction sites of the coexisting oxygen and nitrogenoxides consist of the same oxygen defects, the adsorption probability ofthe nitrogen oxides is much lower than that of the oxygen molecules forreasons of both molecular selectivity and coexisting molecular ratios,so that a large flow of current is required to break down the nitrogenoxides, greatly increasing electric power consumption.

Under these circumstances, the present inventors have already discoveredthat in a chemical reactor it is possible to efficiently process atarget substance with low electric power consumption by making theinternal structure of the cathode a structure in which nanometer-sizedthrough holes are wound through the top of the same layer, and anelectron conductor and an ion conductor on a scale of nanometers to lessthan a micron are distributed together in a dense network, thus reducingthe excess oxygen which is an interfering gas during chemical reactionof the target substance (Japanese Patent Application No. 2001-225034).However, because in this method residual oxygen molecules in the treatedgas which have passed through the upper part of the same layer are stillmore selectively adsorbed and degraded in the reaction sites than arethe nitrogen oxides, the reduction in energy consumption is inadequate.

Moreover, another problem with this method is that the reduction inenergy consumption is inadequate because current needs to be suppliedcontinuously in order to remove coexisting oxygen molecules.

On the other hand, a variety of catalysts are often used in chemicalreactions and oxidation-reduction reactions in particular, includinghomogenous catalysts and heterogenous catalysts. Compared to homogenouscatalysts, heterogenous catalysts which used solid catalysts such asprecious metals and zeolites offer the advantage of easy separation ofthe reactant from the catalyst. However, although heterogenous catalystsallow easy separation of the catalyst, because the raw material and thereactant occupy the same space the necessary product is separated andpurified from unreacted raw material and by-products. A method which hasbeen studied which does not require such separation and purification isone employing a reaction separation membrane (Kagaku Sosetsu No. 41,“Design of high function catalysts,” Japan Chemical Society (1999), p.131).

In a method employing a reaction separation membrane, for example whensynthesizing ethane by an oxygen coupling reaction of methane using anoxygen permeable membrane (3CH₄+½O₂→C₂H₄+H₂O), CH₄ and O₂ are separatedby the oxygen permeable membrane and a suitable catalyst is placed onthe wall of the permeable membrane on the CH₄ side to make aCH₄/catalyst/oxygen permeable membrane/O₂ system, and O₂ is activated onthe catalyst through the oxygen permeable membrane to selectivelysynthesize ethane. When the same reaction is performed using a hydrogenpermeable membrane, the hydrogen permeable membrane is of course placedbetween the CH₄ and O₂ in a CH₄/catalyst/hydrogen permeable membrane/O₂system, but a catalyst having methane dehydrogenation activity needs tobe placed on the wall of the permeable membrane. Membranes used asreaction separation membranes are generally classified into porousmembranes, metal membranes, ion conductor membranes, mixed conductormembranes and the like according to the permeation mechanism of thesubstance permeated. Porous membranes which allow selective permeationof molecules include zeolites and other having nanopores, but synthesisof dense zeolite membranes without pinholes has not been established.

Of the metal membranes, Pd membranes and Pd—Au alloy membranes are usedas reaction separation membranes. Both are used as hydrogen reactionseparation membranes (hydrogen permeable membranes). The concentrationdifference (hydrogen partial pressure difference) between the two sidesof the membrane is used as the drive force of a hydrogen permeablemembrane. Ion conductor membranes (electrolyte membranes) are primarilyhydrogen ion conductors and oxygen ion conductors. When an ion conductormembrane is used as a reaction separation membrane, because the driveforce conducted by the ions is a field gradient electrodes are installedon both sides of the membrane and the electrodes are electricallyconnected to each other with electrical wires. A movement of electronsthrough the lead wire (external circuit) occurs because the ions passthrough the membrane while at the same time neutralizing electriccharge. In a mixed conductor membrane, because both ions and electrons(or electron holes) can be conducted through the membrane there is noneed for electrodes and lead wires to send the electrons. However, theconcentration difference between the two sides of the membrane is usedas the ion drive force.

In particular, in a reaction separation membrane employing an ionconductor membrane, because the field gradient is the drive force areaction can proceed irrespective of the concentration difference.Electrodes are required, however, and a stable substance having electronconductivity which is inactive in oxidation and reduction reactions isused for the electrodes. For example, precious metals such as Pt, Pd andthe like, carbon, and in oxidizing atmospheres LaCoO₃, LaFeO₃, LaMnO₃,LaCrO₃ and other electron conducting oxides and the like are used. Inone example of a reaction separation membrane employing a hydrogen ionconductor membrane, trace acetylene is selectively removed byhydrogenation from ethylene. A reactor such as a C₂H₄₁C₂H₂/Cuelectrode/hydrogen ion conductor membrane/Pt black electrode/H₂ reactoris constructed, and electricity is applied between the two electrodes toselectively hydrogenate (reduce) acetylene, so that acetylene present asan impurity in the ethylene is converted to ethylene and removed. Such areaction occurs because of the strong affinity between acetylene and theCu electrode and the occurrence of atomic hydrogen sent through thehydrogen ion conductor membrane.

In one example of a reaction separation membrane employing a solidelectrolyte membrane having oxygen ion conductivity, nitrogen oxides areremoved by reduction from exhaust gas. One reactor which has beenproposed is a system developed to simultaneously remove surface oxygenand break down nitrogen oxides into oxygen and nitrogen by applyingvoltage to a solid electrolyte sandwiched between electrodes on bothsides. To present the related background art, in the literature ofbackground art it has been proposed that platinum electrodes be formedon both sides of zirconia stabilized with scandium oxide, and voltageapplied to break down into nitrogen oxides and oxygen (J.Electrochemical Soc. 122, 869 (1975)). In the literature of backgroundart it has also been proposed that palladium electrodes be formed onboth sides of zirconia stabilized with yttrium oxide, and voltageapplied to break down into nitrogen and oxygen in a mixed gas ofnitrogen oxides, hydrocarbons and oxygen (J. Chem. Soc. Faraday Trans.91, 1995 (1995)). In this way, in a reaction separation membrane inwhich an ion conductor membrane is provided with electrodes and voltageis applied between the electrodes with the field gradient as the driveforce, not only can the reaction proceed independently of theconcentration difference of the reactant or product, but the types ofions passing through the ion conductor membrane are activated on theelectrode and molecules are easily degraded at the interface between ionconductor and electrode, so that oxidation and reduction can be easilyperformed.

However, in a reaction method using a reaction separation membrane inwhich an ion conductor membrane is provided with electrodes and voltageis applied between the electrodes with the field gradient as the driveforce, oxidation and reduction ability is high but selectivity is low.For example, when removing nitrogen oxides by reduction in a reactor inwhich the aforementioned ion conductor is provided with electrodes, ifoxygen molecules are present they are also broken down into oxygen ions,reducing the efficiency of the reduction removal of nitrogen oxideswhich is the objective of exhaust gas purification. Moreover, while asimple oxidation-reduction reaction using a reducing agent or oxidizingagent with suitable selectivity is also possible, in this case thereducing agent or oxidizing agent needs to be supplied or replacedbecause the reaction cannot continue once this has been exhausted.

DISCLOSURE OF THE INVENTION

Therefore, in light of the aforementioned background art the inventorsarrived at the present invention as a result of exhaustive research intosolving these various problems when they discovered that a reactioncould be made more efficient by forming pairs of reaction sites forperforming simultaneous reduction reactions in a chemical reaction part(for example, a working electrode layer located on the upper part of acathode) and exploiting the selective adsorbability of each for oxygenmolecules and nitrogen oxides.

That is, it is an object of the first embodiment of the presentinvention to solve the aforementioned problems of background art andprovide a chemical reactor capable of efficiently excluding nitrogenoxides with low power consumption wherein the amount of current requiredto break down nitrogen oxides is reduced by using pairs of adsorbentsubstances which are selective for oxygen molecules and nitrogen oxidemolecules to facilitate absorption of nitrogen oxides when excess oxygenis present in exhaust gas.

Moreover, in light of the aforementioned background art the inventorsarrived at the present invention as a result of exhaustive researchaimed at solving these various problems when they discovered that it waspossible to ionize and remove oxygen molecules and reactivate the systemby forming, in a working electrode layer located in the upper part of acathode in the chemical reaction part, local reaction sites which allowgreater efficiency of the chemical reaction by performing oxygenadsorption and adsorption-reduction reactions of nitrogen oxidessimultaneously, and by further applying current to the chemical reactionsystem after adsorption of a fixed amount of oxygen molecules.

That is, it is an object of the second embodiment of the presentinvention to solve the aforementioned problems and provide a chemicalreaction system in which the amount of current required to break downnitrogen oxides is reduced by facilitating absorption of nitrogen oxidesby means of pairs of substances with selective adsorbency for oxygenmolecules and nitrogen oxide molecules when excess oxygen is present inexhaust gas, and in which the chemical reaction system is reactivated atthe same time by application of current after adsorption of a fixedamount of oxygen, and which is capable of efficiently excluding nitrogenoxides with low power consumption.

Moreover, it is an object of the third embodiment of the presentinvention, which was developed with the aim of establishing a newreaction method in an oxidation-reduction reactor capable of solving theaforementioned problems of background art, to provide a novel reactionmethod wherein oxidation or reduction can be achieved with highselectivity using an oxidation-reduction reactor without the need forsupplying or exchanging a reducing agent or oxidizing agent.

Next, the first embodiment of the present invention is explained in moredetail.

The present invention relates to a chemical reaction system forperforming chemical reactions of a target substance, and this chemicalreaction system consists of a chemical reaction part in which theaforementioned chemical reactions of the aforementioned target substanceare performed, and preferably of a barrier layer for impeding ionizationof oxygen.

The chemical reaction part for performing chemical reactions of a targetsubstance is preferably provided with a reduction phase which producesions by supplying electrons to elements contained in the targetsubstance, an ion conduction phase which conducts ions from thereduction phase, and an oxidation phase which discharges electrons fromions conducted by the ion conduction phase.

In the present invention, the target substance is preferably nitrogenoxides in exhaust gas, and the nitrogen oxides are reduced in thereduction phase to generate oxygen ions which are conducted in the ionconduction phase. However, the target substance in the present inventionis not limited to nitrogen oxides. In the chemical reactor of thepresent invention carbon dioxide can be reduced to produce carbonmonoxide, a mixed gas of hydrogen and carbon monoxide can be producedfrom methane, or hydrogen can be produced from water.

The chemical reaction system can be in the form of a pipe, plate,honeycomb or the like for example, but in particular it preferably hasone or multiple through holes with a pair of openings (as in a pipe orhoneycomb), with chemical reaction sites located in each through hole.

In the aforementioned chemical reaction, the reduction phase is porousand should selectively adsorb the substance which is the target of thereaction. Because in reduction electrons are supplied to elementscontained in the target substance to generate ions which are transmittedto the ion conduction phase, it preferably consists of an electricallyconductive substance. For purposes of promoting transmission ofelectrons and ions, it is desirable that it consist of a mixedconductive substance which has the features of both electron conductionand ion conduction, or that it consist of a mixture of an electronconductive substance and an ion conductive substance. The reductionphase may have a layered structure of at least two or more phases ofthese substances.

There are no particular limits on the electrically conductive substanceand ion conductive substance used as the reduction layer. For example,platinum, palladium and other precious metals as well as nickel oxide,cobalt oxide, copper oxide, lanthanum manganite, lanthanum cobaltite,lanthanum chromite and other metal oxides can be used as theelectrically conductive substance. Barium-containing oxides, zeolitesand the like which selectively adsorb the target substance can also beused as the reduction layer. Preferably, at least one or more of theaforementioned substances is used as a mixture with at least one or moreion conductive substances. Ion conductive substances which can be usedinclude for example zirconia stabilized with yttria or scandium oxideand ceria, lanthanum gallate or the like stabilized with gadoliniumoxide or samarium oxide. It is also desirable that the reduction layerconsist of a layered structure of at least two or more phases of theaforementioned substances. More preferably, the reduction layer consistsof a layered structure of two phases, an electrically conductive phaseconsisting of a precious metal such as platinum or the like and a mixedphase of nickel oxide and zirconia stabilized with yttria or scandiumoxide.

The ion conduction phase consists of a solid electrolyte having ionconductivity, and preferably consists of a solid electrolyte havingoxygen ion conductivity. Examples of solid electrolytes having oxygenion conductivity include zirconia stabilized with yttria or scandiumoxide and ceria or lanthanum gallate stabilized with gadolinium oxide orsamarium oxide, but these are not limitations. It is preferable to usezirconia stabilized with yttria or scandium oxide, which has excellentlong-term stability, high conductivity and strength.

The oxidizing phase contains a conductive substance for purposes ofcausing electrons to be released from ions from the ion conductionphase. For purposes of promoting transmission of electrons and ions itis desirable that it consist of a mixed conductive substance having thefeatures of both electron conductivity and ion conductivity or of amixture of an electron conductive substance and an ion conductivesubstance. There are no particular limits on the electrically conductivesubstance and ion conductive substance used as the oxidizing phase. Forexample, platinum, palladium and other precious metals as well as nickeloxide, cobalt oxide, copper oxide, lanthanum manganite, lanthanumcobaltite, lanthanum chromite and other metal oxides can be used as theelectrically conductive substance. For the ion conductive substance,zirconia stabilized with yttria or scandium oxide or ceria or lanthanumgallate stabilized with gadolinium oxide or samarium oxide can be usedfor example.

In order to prevent a supply of electrons necessary for producing oxygenions when oxygen molecules have been surface adsorbed, the barrier layerhas a material and structure which inhibit electrons supplied by thechemical reaction part and particularly the reduction phase fromarriving at the surface. This barrier layer is preferably an ionconductor, mixed electrical conductor or insulator, and when it is amixed electrical conductor the proportion of electron conductivity ispreferably extremely small because when electron conductivity is highthe inhibitory effect on electron conduction is reduced.

A feature of the present invention features is that micro reactionregions where oxidation-reduction reactions of a target substance takeplace are introduced into part of the chemical reaction part by applyingcurrent or an electrical field or heat treatment in a reducingatmosphere or under reduced pressure to the point of contact between theion conduction phase and the electron conduction phase, which iscomposed of a combination of any of an ion conductor, an electronconductor and a mixed electrical conductor. In the present invention,features include the formation as the aforementioned micro reactionregions of interfaces consisting of metal phases of the electronconduction phase, oxygen deficient parts of the ion conduction phase andmicro spaces (gaps) surrounding the contacts of these at the points ofcontact between the electron conduction phase and the ion conductionphase, the introduction into the cathode of the aforementioned microreaction regions where the aforementioned oxidation-reduction reactionstake place, the formation in the top part of the cathode of a workingelectrode layer for managing oxidation-reduction reactions, and theintroduction into the same layer of micro reactions regions nanometersto a micrometer in size where the aforementioned oxidation-reductionreactions take place.

The working electrode located in the top part of the cathode within thechemical reaction part has a structure which allows adsorption of oxygenmolecules and adsorption of a target substance to be performedsimultaneously by separate substances suited to each reaction, inaddition to the highly efficient adsorption and degradation of a targetsubstance discovered previously (Japanese Patent Application No.2001-225034). That is, as shown for example in FIG. 2, a metal phaseproduced by reduction of oxides or present from the beginning(preferably in the form of ultrafine particles (diameter roughly 10 nmto 100 nm) to obtain high reactivity) comes into contact with an oxygendeficient part of a neighboring ion conduction phase and micro spaces afew nm to a few tens of nm or less in size are created around thesepoints of contact, so that oxygen molecules in the introduced target gasand the target substance itself are each selectively adsorbed and brokendown in the oxygen deficient part and the metal phase, respectively, andpower consumption is greatly reduced. If the spaces around the contactpoints are larger than a few tens of nm, they will be larger than themean free paths of the gas molecules, and the separation and adsorptioneffect will gradually decline, or if the formed regions around thecontact points are larger than 100 nm, that is if they are sufficientlylarger than the Debye length and the diffusion length of the oxygendefect, the selective separation and exclusion performance with respectto the target gas will be diminished.

The metal phase and oxygen deficient partly normally form contactsbecause of their production mechanisms, but it is not absolutelynecessary for them to contact in order for the aforementioned selectiveseparation function to apply. That is, even if the oxygen deficient partwhich is formed as a result movement of oxygen in the ion conductionphase due to contribution of electrons from the metal phase (oxide phasebefore reaction) when current is applied loses contact with the metalphase due to effects such as heat shrinkage after formation thereof,this is not a serious impediment to the selective separation function ofthe target gas which is the effect of the present invention.

Such a structure is formed by subjecting the chemical reaction system tocurrent or to heat treatment in a reducing atmosphere or under reducedpressure in addition to the heat treatment processes necessary forforming the structure discovered previously (heat treatment inatmosphere at 1400 to 1450° C. in a zirconia-nickel oxide system). Thatis, a necessary condition for the aforementioned structure is theformation of a reduction phase by application of current at a hightemperature of a few 100° C. or more or heat treatment under reducedpressure or in a hydrogen atmosphere or other reducing atmosphere usingan oxide which is relatively easy to reduce.

In this step, the simultaneous formation of ultrafine structures whichare desirable for efficient reactions occurs more favorably when currentis applied. This includes the production due to volume changes in thecrystal phase from the oxidation-reaction of nanometer to micrometersized holes suited for introduction of the target gas, the formation ofultrafine particle due to re-crystallization of the reduction layer, theformation of oxygen deficient parts in the ion conduction phasethroughout the oxidation-reduction reaction and the like.

The substances which make up such a structure may be a combination of anion conduction phase and an electron conduction phase, a mixture ofconductive phases or a combination of this with an ion conduction phaseor electron conduction phase. When the target substance is nitrogenoxides, a nickel or other metal phase is desirable as the reductionphase because it exhibits highly selective adsorption.

In the present invention, substnces which constitute all or part of theaforementioned micro reaction regions have oxidizing and reducingeffects on the target substance. The aforementioned metal phase consistsfor example of ultrafine particles of a metal phase produced by anoxidation-reduction reaction generated across some or all of an electronconductor or mixed electrical conductor when the aforementioned chemicalreaction system is subjected to current or heat treatment in a reducingatmosphere. Moreover, the aforementioned oxygen deficient part consistsof an oxygen deficient layer produced by an oxygen-reduction reactiongenerated in some or all of an ion conductor or mixed electricalconductor when the aforementioned chemical reaction system is subjectedto current or heat treatment in a reducing atmosphere. Theaforementioned micro reaction regions have a structure in which the ionconductor and electron conductor contact each other directly in at leastone place, or contact each other during the manufacturing process.

The chemical reaction system of the present invention can be prepared bysubjecting the contact points in the aforementioned chemical reactionpart of the ion conduction layer and the electron conduction layer,which are composed of a combination of any of an ion conductor, anelectron conductor and a mixed electrical conductor, to current or toheat treatment in a reducing atmosphere or under reduced pressure so asto introduce into the aforementioned chemical reaction part microreaction regions in which oxidation-reduction reactions of the targetsubstance take place. It is desirable when constructing the interfacesof the aforementioned substances that one or both be in a reduced state.

It is desirable in the present invention that the aforementionedchemical reaction be a conversion reaction of matter or energy, that theaforementioned target substance be nitrogen oxides, that theaforementioned chemical reaction be reduction degradation of nitrogenoxides, and that the aforementioned chemical reaction be represented bythe general formula:Mox+xe→M+x/2O²⁻M→xe+M^(X+)(where M is a metal, O is an oxygen atom and e is an electron)

Next, the second embodiment of the present invention is explained inmore detail.

The present invention relates to a chemical reaction system forperforming chemical reaction of a target substance, with this chemicalreaction system being composed of a chemical reaction part where theaforementioned chemical reaction of the aforementioned target substanceproceeds and preferably of a barrier layer for impeding ionization ofoxygen.

The chemical reaction part for performing chemical reactions of a targetsubstance ideally has a reduction phase which supplies electrons toelements contained in the target substance to generate ions, an ionconduction phase which conducts ions from the reduction phase, and anoxidation phase which releases electrons from ions conducted by the ionconduction phase, but apart from these it is possible as appropriate touse as basic units oxidizing and/or reducing catalysts having functionsequivalent to these, namely oxidation catalysts, reduction catalysts oroxidation-reduction catalysts. In this case, there are no particularlimits on these constituent elements.

In the present invention the target substance is preferably nitrogenoxides in exhaust gas, and nitrogen oxides are reduced in the reductionphase, producing oxygen ions which are conducted in the ion conductionphase. However, the target substance in the present invention is notlimited to nitrogen oxides. The chemical reactor of the presentinvention can be applied to producing carbon monoxide by reduction ofcarbon dioxide, producing a mixed gas of hydrogen and carbon monoxidefrom methane or producing hydrogen from water.

The chemical reaction system may be in the form of a pipe, plate orhoneycomb for example, but in particular it preferably has one ormultiple through holes with a pair of openings (as in a pipe orhoneycomb), with chemical reaction sites located in each through hole.

In the aforementioned chemical reaction part, the reduction phase isporous and should selectively adsorb the substance which is the targetof the reaction. Because in reduction electrons are supplied to elementscontained in the target substance to generate ions which are transmittedto the ion conduction phase, it preferably consists of an electricallyconductive substance. For purposes of promoting transmission ofelectrons and ions, it is desirable that the reduction phase consist ofa mixed conductive substance which has the features of both electronconduction and ion conduction, or that it consist of a mixture of anelectron conductive substance and an ion conductive substance. Thereduction phase may have a layered structure of at least two or morephases of these substances.

There are no particular limits on the electrically conductive substanceand ion conductive substance used as the reduction layer. For example,platinum, palladium and other precious metals and nickel oxide, cobaltoxide, copper oxide, lanthanum manganite, lanthanum cobaltite, lanthanumchromite and other metal oxides can be used as the electricallyconductive substance. Barium-containing oxides, zeolites and the likewhich selectively adsorb the target substance can also be used as thereduction layer. Preferably, at least one or more of the aforementionedsubstances is used as a mixture with at least one or more ion conductivesubstances. Ion conductive substances which can be used include forexample zirconia stabilized with yttria or scandium oxide and ceria,lanthanum gallate or the like stabilized with gadolinium oxide orsamarium oxide. It is also desirable that the reduction layer consist ofa layered structure of at least two or more phases of the aforementionedsubstances. More preferably, the reduction layer consists of a layeredstructure of two phases, an electrically conductive phase consisting ofa precious metal such as platinum or the like and a mixed phase ofnickel oxide and zirconia stabilized with yttria or scandium oxide.

The ion conduction phase consists of a solid electrolyte having ionconductivity, and preferably consists of a solid electrolyte havingoxygen ion conductivity. Examples of solid electrolytes having oxygenion conductivity include zirconia stabilized with yttria or scandiumoxide and ceria or lanthanum gallate stabilized with gadolinium oxide orsamarium oxide, but these are not limitations. It is preferable to usezirconia stabilized with yttria or scandium oxide, which has excellentlong-term stability and is highly conductive and strong.

The oxidation phase contains a conductive substance for purposes ofcausing electrons to be released from ions from the ion conductionlayer. For purposes of promoting transmission of electrons and ions itis desirable that it consist of a mixed conductive substance having thefeatures of both electron conductivity and ion conductivity, or of amixture of an electron conductive substance and an ion conductivesubstance. There are no particular limits on the electrically conductivesubstance and ion conductive substance used as the oxidizing layer. Forexample, platinum, palladium and other precious metals and nickel oxide,cobalt oxide, copper oxide, lanthanum manganite, lanthanum cobaltite,lanthanum chromite and other metal oxides can be used as theelectrically conductive substance. For the ion conductive substance,zirconia stabilized with yttria or scandium oxide or ceria or lanthanumgallate stabilized with gadolinium oxide or samarium oxide can be usedfor example.

The purpose of the barrier layer is to prevent the supply of electronsnecessary for producing oxygen ions when oxygen molecules have beensurface adsorbed. Alternatively, it is provided for the purpose ofpreventing re-oxidation of metals (such as metal nickel) produced byreduction reactions of electrically conductive oxides (such as nickeloxide) by oxygen ions in the chemical reaction part, and has a materialand structure to block electrons supplied by the chemical reaction partand particularly the reduction layer from reaching the surface. Thisbarrier layer is preferably an ion conductor, mixed electrical conductoror insulator, and when it is a mixed electrical conductor the proportionof electron conductivity is preferably extremely small because whenelectron conductivity is high the suppression effect on electronconduction is reduced.

In a chemical reaction system wherein the chemical reaction part iscomposed of an oxygen ion conductor (ion conduction phase), a pairedcathode (reduction phase) and an anode (oxidation phase) with the ionconduction phase therebetween or of an oxidization and/or reductioncatalyst as basic units for performing chemical reactions of a targetsubstance, it is a feature of the present invention that the ability toionize and remove oxygen which impedes reactions when adsorbed by thechemical reaction part is activated either by application of current oran electrical field between the cathode and anode of the aforementionedchemical reaction part, or by heat treatment in a reducing atmosphere orunder reduced pressure. In the present invention, favorable examplesinclude the use as the chemical reaction part of a chemical reactionpart wherein micro reaction regions where oxidation-reduction reactionsof the target substance take place are introduced into part of thechemical reaction part by subjecting the contact points between an ionconduction phase and an electron conduction phase composed of acombination of any of an ion conductor, an electron conductor or a mixedelectrical conductor to current or an electrical field or to heattreatment in a reducing atmosphere or under reduced pressure; or the useas the chemical reaction part of a chemical reaction part having areduction phase which has individual selectivity for both oxygen and thetarget substance and pores a micrometer or less in size for efficientlysupplying and processing the target substance in the reduction phase; orthe use of a chemical reaction part wherein interfaces consisting ofmetal phase parts of the electron conduction phase, oxygen deficientparts of the ion conduction phase and micro spaces (gaps) surroundingthe contact points thereof are formed at the contact points between theelectron conduction phase and the ion conduction phase as theaforementioned micro reaction regions; or the use as the chemicalreaction part of a chemical reaction part wherein micro reaction regionswherein the aforementioned oxidation-reduction reactions take place areintroduced into the cathode as the aforementioned chemical reactionpart; and also the use as the chemical reaction part of a chemicalreaction part having a working electrode layer for performingoxygen-reduction reactions in the upper part of the cathode whereinmicro regions nanometers to a micrometer in size wherein theaforementioned oxidation-reduction takes place are introduced into thesame layer.

The working electrode located in the top part of the cathode within thechemical reaction part has a structure which allows adsorption of oxygenmolecules and adsorption of a target substance to be performedsimultaneously by separate substances suited to each reaction, inaddition to the highly efficient adsorption and degradation of a targetsubstance discovered previously (Japanese Patent Application No.2001-225034). That is, a metal phase produced by reduction of oxides orpresent from the beginning (preferably in the form of ultrafineparticles (diameter 10 to 100 nm) to obtain high reactivity) comes intocontact with an oxygen deficient part (a region of about 5 nm asestimated by calculating from of the Debye length) of a neighboring ionconduction phase, and micro spaces a few nm to a few tens of nm or lessin size are created around these points of contact, so that oxygenmolecules in the introduced target gas and the target substance itselfare each selectively adsorbed and broken down in the oxygen deficientpart and the metal phase, respectively, greatly reducing electricalpower consumption.

Such a structure is formed by subjecting the chemical reaction system tocurrent or to heat treatment in a reducing atmosphere or the like inaddition to the heat treatment processes necessary for forming thestructure discovered previously (heat treatment in atmosphere at 1400 to1450° C. in a zirconia-nickel oxide system). That is, a reduction phaseis formed by application of current under high temperatures of several100° C. or more using an oxide which is relatively easy to reduce. Inthis step, ultrafine structures are formed which are desirable forefficient reactions, including the production due to volume changes inthe crystal phase from the oxidation-reduction reaction of poresnanometers to a micrometer in size which are suitable for introductionof the target gas, the formation of ultrafine particles byre-crystallization of the reduction phase, and the formation of oxygendeficient parts in the ion conduction phase throughout theoxidation-reduction reaction. An example of a local structure formed bythe aforementioned methods which is desirable for the inner structure ofthe working electrode layer is shown in FIG. 4.

Substances which constitute such ultrafine structures are a combinationof an ion conduction phase and an electron conduction phase, a mixtureof conduction phases or a combination of this with an ion conductionphase or electron conduction phase. When the target substance isnitrogen oxides, a nickel or other metal phase is desirable as thereduction phase because it exhibits highly selective adsorption.

In addition to the method of introducing a reducing agent previouslydescribed as background art, a method which has been proposed forreactivating a chemical reaction system is one in which carbon or thelike already forms an integrated structure in the chemical reactionsystem, and the carbon oxidizes during the chemical reaction to reducethe oxidized metal phase (K. Miura et al., Chemical Engineering Science56, 1623 (2001)). However, in these methods reducing agents arerequired, and since reactivation becomes impossible when the reducingagent is exhausted an electrical reactivation method is more desirablefor long term or continuous use of the system.

In the present invention, it is possible to apply current or the likeonly when the performance of the chemical reaction system has declinedin order to ionize and remove by pumping oxygen adsorbed by the oxygendeficient part of the chemical reaction part. Moreover, it is possibleto simultaneously reenergize the reduction phase. In this way, theamount of current in the present invention can be much less than theamount of current required for oxygen pumping in conventionalelectrochemical cell systems.

Reactivation by oxygen pumping in the present invention is performed byapplying current, voltage or heat treatment in a reducing atmosphere orthe like to the chemical reaction system when the system is at 400 to700° C. In the present invention, it is desirable to maintain atemperature of 400 to 700° C. or raise or lower the temperature withinthat temperature range in the aforementioned chemical reaction systemwhile applying current or an electrical field between the cathode andanode for 1 minute to 3 hours. In this case, it is desirable to applycurrent of 5 mA to 1 A or voltage of 0.5 V to 2.5 V to generate anelectrochemical reaction, and to perform current or electrical fieldtreatment at an oxygen partial pressure of 0% to 21% (in atmosphere).The treatment temperature differs depending on the material andstructures which make up the system, but for example a temperature near560° C. is desirable when zirconia stabilized with yttria is used as thesolid electrolyte, and one near 450° C. when ceria is used. The presentinvention provides an activation method for a chemical reaction systemwherein the temperature in the aforementioned chemical reaction systemis maintained at 500° C. or more or raised or lowered within thistemperature range and heat treatment is performed in a reducingatmosphere or under reduced pressure.

In addition to the conditions of treatment temperature and componentmaterials, the conditions of amount of applied current, applied voltage,current time and oxygen partial pressure or total pressure in atmosphereare variable. For example, when zirconia stabilized with yttria is usedas the electrolyte and nickel oxide and zirconia as the workingelectrode materials, the ability to break down nitrogen oxides isrestored to the level before treatment by applying current of 100 mA, 2V for 1 hour (oxygen 10%). The degree of deterioration due to oxygenadsorption is about 20% after 100 hours of continuous operation (withoutcurrent), and performance can be repeatedly restored by theaforementioned current treatment.

Next, the third embodiment of the present invention is explained in moredetail.

In the present invention, the solid electrolyte of the oxygen ionconductor is one with conductivity of 10⁻⁶ Ω⁻¹·cm⁻¹ or more at thetemperature of use. Under 10⁻⁶ Ω⁻¹·cm⁻¹ conductance is so low that thatan oxidized reductant (R) or reduced oxide (RO_(X)) cannot beelectrochemically reduced or oxidized with sufficient speed, and theenergy loss due to internal resistance is too great for practical use.Examples of this solid electrolyte of the oxygen ion conductor includeZrO₂, CeO₂, Bi₂O₃ and LaGaO₃ oxides. A ZrO₂ oxide can be stabilized withY, Sc or the like. A CeO₂ oxide can be stabilized with Gd, Sm or thelike. Multiple oxygen ion conductors can be used as a composite orlaminate. In particular, from the standpoint of stability a ZrO₂ oxideis desirable for removing nitrogen oxides.

Moreover, in the present invention the electrode material consisting ofan electron conductor is one having conductivity of 10⁻⁶ Ω⁻¹·cm⁻¹ ormore at the temperature of use. Under 10⁻⁶ Ω⁻¹·cm⁻¹ conductance is solow that an oxidized reductant (R) or reduced oxide (RO_(X)) cannot beelectrochemically reduced or oxidized with sufficient speed, and theenergy loss due to internal resistance is too great for practical use.Examples of this electrode material consisting of an electron conductorinclude metals, stainless steel, alloys, electron conductive oxides,graphite, glassy carbon and other carbons and the like. Moreover,specific examples include platinum, palladium and other precious metalsand nickel oxide, cobalt oxide, copper oxide, lanthanum manganite,lanthanum cobaltite, lanthanum chromite and other metal oxides. Multipleelectron conductors can be used as a composite or laminate. This mayalso be compounded with the solid electrolyte of the oxygen ionconductor, or a mixed electrical conductor of an oxygen conductor and anelectron conductor may be used. In addition, the electrode material mayalso be compounded with a reductant or oxidant. In particular, from thestandpoint of stability Au, Pt, Ag, Pd, a Ni oxide, a Cu oxide, an Feoxide, a Mn oxide or a combination of these is desirable for purposes ofremoving nitrogen oxides.

The reductant (R) used in the present invention may be any consisting ofa metal or suboxide and having the ability to reduce the oxide AO_(x)(where x is ½ the oxidation number of A) which is the target of thereaction, with no particular limitations, but desirable examples includeMg, Ca and other alkali earth metals, Ti, Cr, Mo, W, Mn, Fe, Co, Ni, Cu,Ag, Zn and other transitional metals, Al, Ga, In, Sn and other metalsand Ti (III), V (IV, III, II), Cr (III, II), Mo (IV, III, II), W (V, IV,III, II), Mn (III), Fe (II), Cu (I) and other suboxides. In particular,from the standpoint of selective reactivity a suboxide or metalcomprising 50% or more of one or more elements selected from Ni, Cu andFe is desirable for removing nitrogen oxides.

The oxide AO_(x) (where x is ½ the oxidation number of A) which can bereduced by the reaction method of the oxidation-reduction reactor of thepresent invention is for example organic matter containing oxygen,oxygen, water, nitrogen oxides or the like, and these can be reduced tothe reduced product AO_(x-y) (where 0<y≦x) in the oxidation-reductionreactor. Reduction of the oxide AO_(x) can proceed as far as the whollyreduced A (y=x), or the partially reduced AO_(x-y) (0<y<x).

The oxidant (RO_(x)) used in the present invention can be any consistingof oxides which is capable of oxidizing the compound A which is thetarget of the reaction, without any particular limitations, and examplesinclude Ti, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, Zn, Pd, Pt, Rh, Au, Irand other transitional metal oxides and Al, Ga, In, Sn and other metaloxides. In particular, from the standpoint of selective reactivity anoxide comprising 50% or more of one or more elements selected from Ni,Cu, Ag and Pt is desirable for oxidation reactions of hydrocarbons andorganochlorine compounds.

A compound A which can be oxidized by an oxidation method using theoxidation-reduction reactor of the present invention is for exampleorganic matter, an organochlorine compound, hydrogen, carbon monoxide,nitrogen oxides, ammonia or the like, and these can be oxidized intoAO_(y) oxides in the aforementioned oxidation-reduction reactor. Inparticular, alcohol or carboxylic acid can be partially oxidized from ahydrocarbon such as methane, ethane, propane, butane or the like, andorganochlorine compounds such as dioxins can be oxidation degraded. Bycontrolling the reaction conditions including reaction time, appliedvoltage and the like, it is possible to take oxidation of compound A asfar as perfectly oxidized AO_(y) (y=x), or as far as the intermediatepartial oxide AO_(x-y) (0<y<x).

When the oxidation-reduction reactor used in the present invention isused as a reduction reactor, an arrangement such as reductant(R)/electrode/oxygen ion conductor/electrode is adopted, or when it isused as an oxidation reactor an arrangement such as electrode/oxygen ionconductor/electrode/oxidant (ROx) is adopted. The reductant (R) andelectrode may be a mixed phase of the two, as may the electrode andoxidant (ROx). In particular, for purposes of removing nitrogen oxidesthe size of the nitrogen oxide reductant is preferably in the range of10 nm to 1 μm. Under 10 nm activity is too high and other oxides arereduced, making it difficult to selectively reduce nitrogen oxides. Over1 μm, the effective surface area of the nitrogen oxide reductant isreduced, and efficient reduction is hard to achieve. Moreover, the layercontaining the reductant (R) or the layer containing the oxidant(RO_(x)) may be a porous body having pores to make the oxidation andreduction reactions more efficient.

The nitrogen oxygen reductant used in the present invention can bemanufactured within the oxidation-reduction reactor by bringing one ormore oxide electron conductors selected from an Ni oxide, Cu oxide, Feoxide and Mn oxide into contact with a solid electrolyte oxygen ionconductor, and applying cathode current to the electron conductor toreduce part of the oxide electron conductor. In the oxidation-reductionreactor of the present invention, in order for the reductant R torestore the oxidized RO_(y) to the original reductant R so as to reducethe oxide AO_(x), RO_(y) can be electrochemically reduced to R byapplication of current to the electrode, or else in order for theoxidant R′O_(x) to restore the reduced R′O_(x-y) to the original oxidantR′O_(x) so as to oxidize the compound A, R′O_(x-y) can beelectrochemically oxidized to R′O_(z) by application of current to theelectrode. Restoration of reductant R or oxidant R′O_(x) by applicationof current between electrodes can be accomplished during theoxidation-reduction reaction, or restoration by application of currentcan be performed after a fixed interval.

In the reaction method using the oxidation-reduction reactor of thepresent invention, the working temperature should be between 300° C. and1000° C. so that sufficient conductivity of the solid electrolyte whichis the oxygen ion conductor can be obtained, but it is also possible toperform the oxidation-reduction reaction at a low temperature such asroom temperature, heating to the aforementioned temperature only whenelectrochemically restoring reductant R or oxidant R′O_(x). Because inthe present invention the reductant (R) or oxidant (RO_(x)) used is anymaterial chosen according to the oxidation or reduction potential of thereaction to be performed in the oxidation-reduction reactor, a highlyselective reaction can be achieved under conditions suited to thedesired reaction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a chemical reaction system according to oneembodiment of the present invention.

FIG. 2 shows one example of a local structure which is desirable as theinternal structure of the working electrode layer.

FIG. 3 is a chart in which the relationship between removal performanceof nitrogen oxides and amount of applied current in a chemical reactionsystem according to the present invention is compared with the resultsof existing research and the performance of a reactor of a previousapplication of the inventors.

FIG. 4 shows one example of a local structure which desirable as theinternal structure of the working electrode layer.

FIG. 5 shows how ability to purify nitrogen oxides is restored byapplication of current.

LIST OF ELEMENTS

-   1 Barrier layer-   2 Working electrode layer-   3 Cathode (reduction phase)-   4 Ion conduction phase-   5 Anode (oxidation phase)-   6 Chemical reaction part-   7 Chemical reaction system

BEST MODE FOR CARRYING OUT THE INVENTION

Examples of the first embodiment of the present invention are explainedbelow using the drawings. FIG. 1 is a block diagram of a chemicalreaction system according to one embodiment of the present invention. Inchemical reaction part 6 which makes up chemical reaction system 7,working electrode 2, cathode (reduction layer) 3, ion conduction layer 4and anode (oxidation layer) 5 are arranged in upstream-to-downstreamorder with respect to the flow of gas which is the target of thereaction, with barrier layer 1 placed upstream therefrom. In otherwords, the target gas passes through in order from 1 to 5.

FIG. 2 shows one example of a micro reaction region of a desirableinternal local structure in working electrode layer 2 according to thepresent invention. A more detailed explanation is given below withnitrogen oxides used as the target substance.

EXAMPLE 1

Zirconia stabilized with yttria was used as ion conduction phase 4, in adisk form with a diameter of 20 mm and a thickness of 0.5 mm. Reductionphase 3 was a mixed layer of platinum and zirconia, while workingelectrode layer 2 was a film consisting of a mixture of nickel oxide andyttria-stabilized zirconia. A platinum film was first screen printed toan area of about 1.8 cm² on one side of ion conduction phase 4, andformed by heat treatment at 1200° C. A mixed film of nickel oxide andyttria-stabilized zirconia was screen printed on the platinum film withthe same area as the platinum film, and formed by heat treatment at1450° C. The compounding ratio of nickel oxide to yttria-stabilizedzirconia was 6:4 mole. Once a platinum film had been screen printed toan area of 1.8 cm² on the other side of ion conduction phase 4 having aformed reduction phase, it was formed by heat treatment at 1200° C. tomake oxidation phase 5. Barrier layer 1 was formed on the upper part ofworking electrode layer 2 with a thickness of about 3 microns by screenprinting and heat treatment at 1400° C. using yttria-stabilizedzirconia. The temperature was then raised to 650° C. as current of 1.2 Vto 25 mA was passed applied cathode 3 and anode 5, and maintained forone hour after which the current was stopped and the system cooled.

The method of treating nitrogen oxides with a chemical reaction systemof the present invention formed as above is shown below. Chemicalreaction system 7 was placed in a target gas, reduction phase 3 andoxidation phase 5 were fixed with platinum wires as lead wires andconnected to a direct current source, and direct current voltage wasapplied to start the flow of current. Evaluation was performed in areaction temperature range of 500° C. to 600° C. Helium balanced modelexhaust gas containing 1000 ppm nitrogen monoxide and 2% oxygen wassupplied at a flow rate of 50 ml/min as the target gas. The nitrogenoxide concentration in the target gas before and after flow to thechemical reactor was measured by a chemiluminescent NOx meter, whilenitrogen and oxygen concentrations were measured by gas chromatography.The exclusion rate of nitrogen oxides was derived from the amount ofdecrease in nitrogen oxides, and the current density and electric powerconsumption were measured when the exclusion rate reached 50%.

The reaction temperature of the chemical reactor was raised to 600° C.,and current was supplied to the chemical reaction part. As the amount ofcurrent rose the exclusion rate of the nitrogen oxides also rose, andnitrogen oxides fell to about 50% when current density was 31 mA/cm² andpower consumption was 61 mW/cm². In FIG. 3, the performance sequence ofa chemical reactor of the present invention is shown in comparison withthe performance of a reactor of a previous application and the resultsof existing research. It is clear from this figure that the performanceof the chemical reactor of the present application is superior to theresults of existing research.

EXAMPLE 2

In the energizing and heating process of the final stage of preparing achemical reaction system as in Example 1, four cycles were performed inwhich current of 1.2 V to 25 mA was supplied between cathode 3 and anode5 as the temperature was raised to 650° C. and maintained for 1 hourafter which the current was stopped, followed by gradual cooling, andthe relationship between number of cycles and ability to processnitrogen oxides was investigated. With 2 cycles a nitrogen oxide removalrate of 50% was achieved at a current density of 25 mA/cm² and anelectric energy consumption of 49 mW/cm², while with 3 cycles this fellto a current density of 24 mA/cm² and an electric energy consumption of47 mW/cm², but with 4 cycles the results were similar to those achievedwith 3 cycles.

EXAMPLE 3

Changes in reactivity in a chemical reaction system prepared as inExample 1 were investigated relative to amount of coexisting oxygenimpeding the reaction and concentration of nitrogen oxides which werethe target substance. Under the same experimental conditions as inExample 1, current density and electric energy consumption at 50%degradation were measured (a) with the oxygen amount increased from 2%to 10% and (b) with the nitrogen oxide concentration reduced from 1000ppm to 500 ppm. The results were (a) current density 55 mA/cm², electricenergy consumption 150 mW/cm² and (b) current density 20 mA/cm²,electric energy consumption 37 mW/cm², respectively, showing that in thechemical reaction system of the present invention relative processingability is improved even with a large amount of coexisting oxygen, whilea dramatic improvement in performance is seen with respect to a weaknitrogen oxide concentration.

Examples of the second embodiment of the present invention are explainedbelow using the figures. FIG. 1 is a block diagram of a chemicalreaction system according to one embodiment of the present invention. Inchemical reaction part 6 which makes up chemical reaction system 7, theworking electrode, cathode (reduction layer), ion conduction layer andanode (oxidation layer) are arranged in upstream-to-downstream orderfrom 2 to 5 with respect to the flow of gas which is the target of thereaction, with barrier layer 1 placed upstream therefrom. In otherwords, the target gas passes through in order from 1 to 5.

A more detailed explanation is given below with nitrogen oxides used asthe target substance.

EXAMPLE 4

Zirconia stabilized with yttria was used as ion conduction phase 4, indisk form with a diameter of 20 mm and a thickness of 0.5 mm. Reductionphase 3 was a mixed layer of platinum and zirconia, while workingelectrode layer 2 was a film consisting of a mixture of nickel oxide andyttria-stabilized zirconia. A platinum film was first screen printed toan area of about 1.8 cm² on one side of ion conduction layer 4, andformed by heat treatment at 1200° C. A mixed film of nickel oxide andyttria-stabilized zirconia was screen printed on the platinum film withthe same area as the platinum film, and formed by heat treatment at1450° C. The compounding ratio of nickel oxide to yttria-stabilizedzirconia was 6:4 mole. Once a platinum film had been screen printed toan area of 1.8 cm² on the other side of ion conduction phase 4 having aformed reduction phase, it was formed by heat treatment at 1200° C. tomake oxidation phase 5. Barrier layer 1 was formed on the upper part ofworking electrode layer 2 with a thickness of about 3 microns by screenprinting and heat treatment at 1400° C. using yttria-stabilizedzirconia. The temperature was then raised to 650° C. as current of 1.2 Vto 25 mA was passed between cathode 3 and anode 5, and retained for onehour after which the current was stopped and the system cooled.

The method of treating nitrogen oxides with a chemical reaction systemof the present invention formed as above is shown below. Chemicalreaction system 7 was placed in a target gas, reduction phase 3 andoxidation phase 5 were fixed with platinum wires as lead wires andconnected to a direct current source, and direct current voltage wasapplied to start the flow of current. System performance with currentwas evaluated at 600° C., and without current at a reaction temperatureof 350° C. Helium balanced model exhaust gas containing 1000 ppmnitrogen monoxide and 2% oxygen was supplied at a flow rate of 50 ml/minas the target gas. The nitrogen oxide concentration in the target gasbefore and after flow to the chemical reaction system was measured by achemiluminescent NOx meter, while nitrogen and oxygen concentrationswere measured by gas chromatography. The purification rate of nitrogenoxides was derived from the amount of decrease in nitrogen oxides, andthe current density and electric power consumption were measured whenthe purification rate reached 50%.

That is, the chemical reactor was heated to a reaction temperature of600° C. when measurement was initiated, and current was supplied to thechemical reaction part. At this time, the nitrogen oxide purificationrate rose as the amount of current increased, and nitrogen oxidesdecreased to about 50% when current density was 31 mA/cm² and electricpower consumption was 61 mW/cm².

Current to this chemical reaction system was stopped 1 hour after beinginitiated, while measurement of the degradation rate of nitrogen oxideswas continued. The degradation rate of nitrogen oxides fell about 10%immediately after cessation of current, but then tended to fall slowly,falling only 5% or less after a total of 5 days (120 hours) ofcontinuous measurement, showing that the exclusion rate is reduced overtime. When the amount of electric power required for an exclusionreaction of nitrogen oxides over a total of 120 hours was compared withvalues calculated at an exclusion rate of 35%, it was found that withthe present invention it is reduced to about 1/84 or less of thatrequired by continuous current.

EXAMPLE 5

In order to investigate applicability to conditions of actual use,ability to remove nitrogen oxides was investigated with the oxygen levelraised from 2% to 10% and the concentration of nitrogen oxides reducedfrom 1000 ppm to 500 ppm in a chemical reaction system of the samecomposition as in Example 4. Current was supplied to the system 3 timesfor 10 minutes each under the same temperature and electric powerconditions as in Example 4. As shown in FIG. 5, the degradation rate ofnitrogen oxides decreased 15% or more immediately after initiation ofmeasurement, and had fallen to a nitrogen oxide degradation rate of lessthan 30% about 20 hours after initiation of measurement, but thendecreased gradually and was in rough equilibrium after about 100 hours.After 200 hours, roughly the same changes over time in the nitrogenoxide degradation rate were achieved by once again applying current.

EXAMPLE 6

Activation of the system by treatment in a reducing atmosphere wasevaluated in a chemical reaction system of the same composition as inExample 4. When in a chemical reaction system in which a powerconsumption of roughly 68 mW/cm² was required for 50% nitrogen oxidedegradation with 2% coexisting oxygen, a system operating temperature of650° C. and a nitrogen oxide concentration of 1000 ppm, the temperaturewas raised to 800° C. 48 hours after current was stopped (at which pointthe nitrogen oxide degradation rate had fallen to 38%), a reducing gasof 5% hydrogen, 95% argon was supplied for 10 hours, and nitrogen oxidepurification performance was measured, performance was found to haveimproved by about 2%.

Next, the third embodiment of the present invention is explained indetail based on examples, but the present invention is not limited tothese examples alone.

EXAMPLE 7

Zirconia stabilized with yttrium oxide was used as a solid electrolytehaving oxygen ion conductivity, in disk form with a diameter of 20 mmand a thickness of 0.5 mm. The electrode layer was a composite ofplatinum and zirconia stabilized with yttrium oxide, with a volume ratioof 40:60. The reductant layer was a composite of iron, platinum andzirconia stabilized with yttrium oxide with a volume ratio of 30:30:40prepared as the upper layer of the aforementioned electrode layer. Theelectrode layer which was the counter electrode was prepared as acomposite of platinum and zirconia stabilized with yttrium oxide with avolume ratio of 60:40 to the same area as the opposite surface of thesolid electrolyte disk.

An oxygen reduction reactor prepared in this way was used to synthesizeH₂ by reduction of H₂O in the presence of 10% CO₂. By applying currentbetween the electrodes under temperature conditions of 400 to 800° C.,it was possible even in the presence of CO₂ to selectively reduce H₂Oand manufacture H₂ with a conversion rate of 90%. Moreover, current wassupplied to the electrodes to restore the reductant, the current wasstopped, the same H₂O was selectively reduced with a conversion rate of50 to 80% of H₂, and the reductant was restored by application ofcurrent between the electrodes when the conversion rate fell to 50% orless. After restoration, the current was stopped and a reaction wasperformed as above, and it was possible to again manufacture H₂ with aconversion rate of 50 to 80%.

EXAMPLE 8

Zirconia stabilized with yttrium oxide was used as a solid electrolytehaving oxygen ion conductivity, in disk form with a diameter of 20 mmand a thickness of 0.5 mm. The electrode layer was a composite ofplatinum and zirconia stabilized with yttrium oxide, with a volume ratioof 40:60. The nitrogen oxide reductant layer was a composite of nickeloxide and zirconia stabilized with yttrium oxide with a volume ratio of40:60 prepared as the upper layer of the aforementioned electrode layer.The electrode layer which was the counter electrode was prepared as acomposite of platinum and zirconia stabilized with yttrium oxide with avolume ratio of 60:40 to the same area as the opposite surface of thesolid electrolyte disk. Current was supplied between the electrodes at500° C. to reduce some of the nickel oxide of the nitrogen oxidereductant layer into metal nickel particles 100 nm in size and form thefinal nitrogen oxide reductant layer.

1000 ppm NO as the nitrogen oxides was reduced and removed in thepresence of 5% O₂ by an oxidation-reduction reactor prepared in thisway. NO was selectively reduced at a conversion rate of 70% even in thepresence of O₂ by applying current between the electrodes undertemperature conditions of 400 to 700° C. Moreover, current was suppliedto the electrodes to restore the reductant, the current was stopped, thesame NO was selectively reduced with a conversion rate of 50 to 80%, andthe reductant was restored by application of current between theelectrodes when the conversion rate fell to 50% or less. Afterrestoration, the current was stopped and a reaction was performed asabove, and it was possible to again manufacture NO with a conversionrate of 50 to 80%.

EXAMPLE 9

Zirconia stabilized with yttrium oxide was used as a solid electrolytehaving oxygen ion conductivity, in disk form with a diameter of 20 mmand a thickness of 0.5 mm. The electrode layer was a composite oflanthanum manganite and zirconia stabilized with yttrium oxide, with avolume ratio of 50:50. The nitrogen oxide reductant layer was acomposite of nickel oxide and zirconia stabilized with yttrium oxidewith a volume ratio of 40:60 prepared as the upper layer of theaforementioned electrode layer. The electrode layer for the counterelectrode was prepared from La—Sr—Ca—Fe—O so as to have the same area asthe opposite surface of the solid electrolyte disk. Current was appliedbetween the electrodes at 500° C. to convert some of the nickel oxide ofthe nitrogen oxide reductant layer to metal nickel particles 50 nm insize and form the final nitrogen oxide reductant layer.

1000 ppm NO as the nitrogen oxides was reduced and removed in thepresence of 10% O₂ with an oxidation-reduction reactor prepared in thisway. It was possible to selectively reduce NO with a conversion rate of65% even in the presence of O₂ by applying current between theelectrodes under temperature conditions of 400 to 700° C. Moreover,current was supplied to the electrodes to restore the reductant, thecurrent was stopped, the same NO was selectively reduced with aconversion rate of 50 to 80%, and the reductant was restored byapplication of current between the electrodes when the conversion ratefell to 50% or less. After restoration, the current was stopped and areaction was performed as above, and it was possible to againmanufacture NO with a conversion rate of 50 to 80%.

EXAMPLE 10

Zirconia stabilized with yttrium oxide was used as a solid electrolytehaving oxygen ion conductivity, in disk form with a diameter of 20 mmand a thickness of 0.5 mm. The electrode layer was a composite ofplatinum and zirconia stabilized with yttrium oxide with a volume ratioof 40:60. The oxidation layer was a composite of silver oxide, platinumand zirconia stabilized with yttrium oxide with a volume ratio of30:30:40 prepared as the upper layer of the aforementioned electrodelayer. The electrode layer which was the counter electrode was preparedas a composite of platinum and zirconia stabilized with yttrium oxidewith a volume ratio of 60:40 to the same surface area as the oppositesurface of the solid electrolyte disk.

CH₃OH was synthesized by partial oxidation of CH₄ in the presence of 5%CO using an oxidation-reduction reactor prepared in this way. Byapplying current between the electrodes under temperature conditions of400 to 600° C., it was possible to manufacture CH₃OH with a conversionrate of 95% by selective oxidation of CH₄ even in the presence of CO.Moreover, current was applied between the electrodes to restore theoxidant, the current was stopped, the same CH₄ was selectively oxidizedto manufacture CH₃OH with a conversion rate of 60 to 80%, and currentwas supplied between the electrodes to restore the oxidant when theconversion rate fell to 60% or less. After restoration the current wasstopped, and when the same reaction was performed as above it waspossible to again manufacture CH₃OH with a conversion rate of 60 to 80%.

EXAMPLE 11

Zirconia stabilized with yttrium oxide was used as a solid electrolytehaving oxygen ion conductivity, in disk form with a diameter of 20 mmand a thickness of 0.5 mm. The electrode layer was a composite ofplatinum and zirconia stabilized with yttrium oxide with a volume ratioof 40:60. The oxidation layer was a composite of copper oxide, platinumand zirconia stabilized with yttrium oxide with a volume ratio of40:30:30 prepared as the upper layer of the aforementioned electrodelayer. The electrode layer which was the counter electrode was preparedas a composite of lanthanum manganite and zirconia stabilized withyttrium oxide with a volume ratio of 60:40 to the same surface area asthe opposite surface of the solid electrolyte disk.

Dioxin was oxidation degraded in the presence of 10% CO using anoxidation-reduction reactor prepared as above. By supplying currentbetween the electrodes under temperature conditions of 400 to 600° C.,it was possible to selectively oxidize and degrade dioxin with aconversion rate of 80% even in the presence of CO. Moreover, current wasapplied between the electrodes to restore the oxidant, the current wasstopped, the same dioxin was selectively oxidation degraded with aconversion rate of 40 to 70%, and current was supplied between theelectrodes to restore the oxidant when the conversion rate fell to 40%or less. After restoration the current was stopped, and when the samereaction was performed as above it was possible to again oxidationdegrade dioxin with a conversion rate of 40 to 70%.

EXAMPLE 12

A CeO₂ oxide stabilized with Sm was used as a solid electrolyte havingoxygen ion conductivity, in disk form with a diameter of 20 mm and athickness of 0.5 mm. The electrode layer was a composite of lanthanummanganite and CeO₂ oxides stabilized with Sm, with a volume ratio of50:50. The oxidizing layer was a composite of silver oxide, tungstenoxide and CeO₂ oxides stabilized with Sm with a volume ratio of20:20:30:30, prepared as the upper layer of the aforementioned electrodelayer. The electrode layer which was the counter electrode was preparedas a composite of lanthanum manganite and CeO2₂ oxides stabilized withSm with a volume ratio of 60:40 to the same area as the opposite surfaceof the solid electrolyte disk.

CH₃COOH was synthesized by partial oxidation of CH₃CH₂OH in the presenceof 5% CH₄ using an oxidation-reduction reactor prepared as above. Byapplying current between the electrodes under temperature conditions of400 to 600° C., it was possible to manufacture CH₃COOH with a conversionrate of 70% by selective partial oxidation of CH₃CH₂OH even in thepresence of CH₄. Moreover, current was applied between the electrodes torestore the oxidant, the current was stopped, the same CH₃CH₂OH wasselectively partially oxidized to manufacture CH₃COOH with a conversionrate of 50 to 70%, and current was supplied between the electrodes torestore the oxidant when the conversion rate fell to 50% or less. Afterrestoration the current was stopped, and when the same reaction wasperformed as above it was possible to again manufacture CH₃COOH with aconversion rate of 50 to 70%.

INDUSTRIAL APPLICABILITY

As discussed above, the following effects are achieved by the firstembodiment of the present invention.

(1) A chemical reaction system can be provided which is capable ofefficiently processing a target substance even in the presence of excessoxygen which interferes with chemical reaction of the target substance.

(2) The amount of current necessary to degrade nitrogen oxides can bereduced, and nitrogen oxides can be efficiently excluded with lowelectric power consumption.

(3) Micro reaction regions where oxidation and reduction reactions of atarget substance take place can be introduced into part of the chemicalreaction part of the aforementioned chemical reaction system.

(4) A chemical reaction system can be provided having a chemicalreaction part wherein interfaces consisting of metal phase parts of theelectron conduction phase, oxygen deficient parts of the ion conductionphase and micro spaces (gaps) surrounding the contact points thereof areformed at the contact points between the electron conduction phase andthe ion conduction phase.

Moreover, the following effects are achieved by the second embodiment ofthe present invention.

(1) A chemical reaction system can be provided capable of efficientlyprocessing a target substance with low electric power consumption evenin the presence of excess oxygen which interferes with chemical reactionof the target substance.

(2) Nitrogen oxides can be excluded efficiently with low electric powerconsumption.

(3) The chemical reaction system can be reactivated.

(4) An energy-saving electrochemical reaction system can be providedwherein the chemical reaction part can be reactivated and used byapplying current or an electrical field at intervals of time.

Moreover, embodiment 3 of the present invention relates to a reactionmethod for oxidation and reduction reactions, and the effects describedbelow are achieved by the present invention.

(1) A reaction method can be provided for oxidizing or reducing withhigh selectivity using an oxidation-reduction reactor without the needof a supply or exchange of a reducing agent or oxidizing agent.

(2) Because in the reaction method using the oxidation-reduction reactorof the present invention the reductant or oxidant is selected accordingto the reaction from various substances having oxidizing or reducingability, a desired substance such as organic matter, an organochlorinecompound, hydrogen, carbon monoxide, nitrogen oxides, ammonia, nitrogenoxides or the like can be oxidized with high selectivity.

(3) The present invention can be used for example to synthesize usefulsubstances such as hydrogen, methanol, acetic acid and the like, toremove impurities, and to remove harmful substances such as dioxins andnitrogen oxides in exhaust gas.

(4) Since in the method of the present invention the reductant oroxidant can be restored by application of current, a low-maintenancereaction method can be provided wherein these do not need to beexchanged.

1. A chemical reaction system for performing chemical reactions of atarget substance comprising a chemical reaction part which is composedof an oxygen ion conductor (ion conduction phase) and two electrodes, acorresponding cathode (reduction phase) and anode (oxidation phase) withthe ion conduction phase therebetween, as basic units, wherein microreaction regions where oxidation-reduction reactions of a targetsubstance take place are introduced into part of the chemical reactionpart by applying current, voltage, or heat treatment in a reducingatmosphere or under reduced pressure to the points of contact betweenthe ion conduction phase and an electron conduction phase, which iscomposed of a combination of any of an ion conductor, electron conductoror mixed electrical conductor in the chemical reaction part.
 2. Thechemical reaction system according to claim 1, wherein interfacesconsisting of a metal phase of the electron conduction phase, an oxygendeficient part of the ion conduction phase and micro spaces (gaps)surrounding the contact points of these are formed as the micro reactionregions at the points of contact between the electron conduction phaseand the ion conduction phase.
 3. The chemical reaction system accordingto claim 1, wherein micro reaction regions where the oxidation-reductionreactions take place are introduced into the cathode.
 4. The chemicalreaction system according to claim 1, wherein a working electrode layerto manage oxidation-reduction reactions is formed in the upper part ofthe cathode, and micro reaction regions nanometers to a micrometer insize where the oxidation-reduction reactions take place are introducedinto the same layer.
 5. The chemical reaction system according to claim1, wherein a substance making up all or part of the micro reactionregions has an oxidizing or reducing effect on the target substance. 6.The chemical reaction system according to claim 1, wherein the metalphase consists of ultrafine particles of a metal phase produced by anoxidation-reduction reaction generated across some or all of an electronconductor or mixed electrical conductor by subjecting the chemicalreaction system to current or heat treatment in a reducing atmosphere.7. The chemical reaction system according to claim 1, wherein the oxygendeficient part consists of an oxygen deficient layer produced by anoxidation-reduction reaction generated across some or all of an ionconductor or mixed electrical conductor by subjecting the chemicalreaction system to current or heat treatment in a reducing atmosphere.8. The chemical reaction system according to claim 1, having a structurein which the ion conductor and electron conductor contact each other inat least one place to constitute the micro reaction regions, or in whichthey contact each other in the manufacturing process thereof.
 9. Thechemical reaction system according to claim 1, wherein a barrier layerof a substance capable of interrupting electron conduction is includedon the pathway which the target substance travels from theelectrochemical cell surface to the space where the chemical reactiontakes place.
 10. The chemical reaction system according to claim 1,wherein the chemical reaction is a conversion reaction of matter orenergy.
 11. The chemical reaction system according to claim 1, whereinthe target substance is nitrogen oxides.
 12. The chemical reactionsystem according to claim 10, wherein the chemical reaction is reductiondegradation of nitrogen oxides.
 13. The chemical reaction systemaccording to claim 9, wherein a chemical reaction represented by thefollowing general formula:Mox+xe→M+x/2O²⁻M→xe+M^(x+) (where M is a metal, 0 is an oxygen atom and e is anelectron) is generated in the chemical reaction system.
 14. A method formanufacturing the chemical reaction system as claimed in claim 1comprising introducing micro reaction regions where oxidation-reductionreactions of a target substance take place into a chemical reaction partby applying current or heat treatment in a reducing atmosphere to thepoints of contact between an ion conduction phase and an electronconduction phase composed of a combination of any of an ion conductor,an electron conductor and a mixed electrical conductor in the chemicalreaction part.
 15. The method according to claim 14, wherein when thesubstances contact each other to form an interface, one or both of themis in a reduced state.
 16. A method for activating a chemical reactionsystem, wherein in the chemical reaction system according to claim 1,pairs are formed of metal phase parts of an electron conduction phase ormixed electrical conduction phase and oxygen deficient parts of an ionconduction phase or mixed electrical conduction phase.
 17. A chemicalreaction system in which the chemical reaction part is composed of 1) anoxygen ion conductor (ion conduction phase), a corresponding cathode(reduction phase) and anode (oxidation phase) with the ion conductionphase therebetween or 2) an oxidizing and/or reducing catalyst as basicunits for performing chemical reactions of a target substance, whereinthe chemical reaction part is subjected to current or voltage or to heattreatment in a reducing atmosphere or under reduced pressure to activatethe ability to ionize and remove oxygen which impedes reactions whenadsorbed by the chemical reaction part.
 18. The chemical reaction systemaccording to claim 17, wherein a chemical reaction part having areduction layer which has selectively for both oxygen and a targetsubstance, respectively and holes a micrometer or less in size which arenecessary for efficiently supplying and processing the target substancein the reduction phase is used as the chemical reaction part.
 19. Thechemical reaction system according to claim 17, wherein a chemicalreaction part having micro reaction regions where oxidation-reductionreactions of a target substance take place introduced into part of thechemical reaction part by applying current, voltage, or heat treatmentin a reducing atmosphere or under reduced pressure to the points ofcontact between an ion conduction phase and an electron conduction phasecomposed of a combination of any of an ion conductor, an electronconductor and a mixed electrical conductor is used as the chemicalreaction part.
 20. The chemical reaction system according to claim 19,wherein a chemical reaction part is used in which interfaces consistingof metal parts of the electron conduction phase, oxygen deficient partsof the ion conduction phase and micro spaces (gaps) surrounding thepoints of contact of these are formed as the micro reaction regions. 21.The chemical reaction system according to claim 19, wherein a chemicalreaction part having micro reaction regions where theoxidation-reduction reactions take place introduced into the cathode isused as the chemical reaction part.
 22. The chemical reaction systemaccording to claim 17, wherein a chemical reaction part having a workingelectrode layer for managing oxidation-reduction reactions in the upperpart of the cathode and micro reaction regions nanometers to amicrometer in size where the oxidation-reduction reactions take placeintroduced into the same layer is used as the chemical reaction part.23. The chemical reaction system according to claim 17, wherein thetarget substance is nitrogen oxides.
 24. The chemical reaction systemaccording to claim 22, wherein the chemical reaction is reductiondegradation of nitrogen oxides.
 25. A method for using a chemicalreaction system for performing chemical reactions of a target substanceas claimed in claim 17, comprising maintaining the temperature of thesystem at 400 to 700° C., or raising or lowering the temperature withinthis temperature range in the chemical reaction system, and applyingcurrent or voltage at intervals of time to activate the chemicalreaction part.
 26. A method for activating a chemical reaction systemfor performing chemical reactions of a target substance as claimed inclaim 17, comprising maintaining the temperature of the system at 400 to700° C., or raising or lowering the temperature within this temperaturerange in the chemical reaction system, and applying current or voltagetreatment between the cathode and anode for 1 minute to 3 hours.
 27. Themethod for activating a chemical reaction system according to claim 26,wherein an electrochemical reaction is generated by applying 5 mA to 1 Acurrent or 0.5 V to 2.5 V voltage.
 28. The method for activating achemical reaction system according to claim 26, wherein current orvoltage treatment is performed in an oxygen partial pressure of 0% to21% (in atmosphere).
 29. A method for activating a chemical reactionsystem for performing chemical reactions of a target substance asclaimed in claim 17, comprising maintaining the temperature of thesystem at 500° C. or more, or raising or lowering the temperature withinthis temperature range in the chemical reaction system, and heattreating the system in a reducing atmosphere or under reduced pressure.30. A reaction method which is an oxidation-reduction reaction methodusing an oxidation-reduction reactor composed of a solid electrolyteoxygen ion conductor and at least an electrode consisting of an electronconductor, comprising producing the cathode provided with reductant (R)and reduction product AO_(x-y) (where 0<y≦x) by an oxidation-reductionreaction of oxide AO_(x) and reductant (R) based on the reaction formulaAO_(x)+R→RO_(y)+AO_(x-y), or producing the anode provided with oxidant(R′O_(x)) and oxide AO_(y) by an oxidation-reduction reaction ofcompound A and oxidant (R′O_(x)) based on the reaction formulaA+R′O_(x)→R′O_(x-y)+AO_(y).
 31. The reaction method according to claim30, wherein the cathode is provided with a reductant (R) consisting of ametal or suboxide, (1) oxide AO_(x) (where x is ½ the oxidation numberof A) is introduced into the reactor and the reduction product AO_(x-y)(where 0<y≦x) is produced by an oxidation-reduction reaction of oxideAO_(x) and reductant (R) based on the reaction formulaAO_(x)+R→RO_(y)+AO_(x-y), and (2) current is supplied to the electrodeand the oxidized reductant (RO_(y)) is reduced by the electrochemicalreaction represented by the reaction formulas y2e⁻+RO_(y)→R+yO²⁻(cathode) and yO²⁻→y ½O²↑+y2e⁻ (anode) to restore the reductant (R). 32.The reaction method according to claim 31, wherein current is suppliedto the electrode to restore the reductant (R) either after orsimultaneously during production of the reduction product AO_(x-y)(where 0<y≦x) by an oxidation-reduction reaction of oxide AO_(x) andreductant (R).
 33. The reaction method according to claim 32, whereinthe reductant (R) is a nitrogen oxide reductant, and a reduction productof N₂ is produced by an oxidation-reduction reaction of the nitrogenoxide reductant and the nitrogen oxide NO_(x) based on the reactionformula NO_(x)+R→RO_(x)+x/2N₂ to remove the NO_(x).
 34. The reactionmethod according to claim 33, wherein the oxidation-reduction reactorcomprises a nitrogen oxide reductant consisting of metals or suboxides50% or more of which comprises one or more elements selected from Ni, Cuand Fe, an electrode consisting of an electron conductor which is one ormore selected from Au, Pt, Ag, Pd, a Ni oxide, a Cu oxide, a Fe oxideand a Mn oxide, and a solid electrolyte oxygen ion conductor consistingof zirconium oxide.
 35. The reaction method according to claim 33,wherein the size of the nitrogen oxide reductant is 10 nm to 1 μm. 36.The reaction method according to claim 33, wherein an oxide electronconductor which is one or more selected from a Ni oxide, a Cu oxide, anFe oxide and a Mn oxide is brought into contact with a solid electrolyteoxygen ion conductor, and cathode current is supplied to the electronconductor to reduce part of the oxide electron conductor and form anitrogen oxide reductant 10 nm to 1 μm in size.
 37. The reaction methodaccording to claim 30, wherein the anode is provided with an oxidant(R′O_(x)) consisting of an oxide, (1) compound A is introduced into thereactor and oxide AO_(y) is produced by an oxidation-reduction reactionof compound A and oxidant (R′O_(x)) based on the reaction formulaA+R′O_(x)→R′O_(x-y)+AO_(y), and (2) current is supplied to the electrodeand the reduced oxide R′O_(x-y) is oxidized by the electrochemicalreaction represented by the reaction formulasyO²⁻+R′O_(x-y)→R′O_(x)+y2e⁻ (anode) and y2e⁻+O₂→y2O²⁻ (cathode) torestore the oxidant (R′O₂).
 38. The reaction method according to claim37, wherein current is supplied to the electrode to restore the oxidant(R′O_(x)) either after or simultaneously during production of the oxideAO_(y) by an oxidation-reduction reaction of compound A and oxidant(R′O_(x)).
 39. The reaction method according to claim 37, whereincompound a is a hydrocarbon or organochlorine compound.